"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." John 3:16
The above verse is the plainest explanation of the Gospel I have yet found in the Bible. But many would choose to misinterpret this verse to read out of it evidence that Christ died for every last human being on the Earth. However, by comparing this verse to other parts of the Bible (as we must, see 1 Corinthians 2:13) we can see very definitively that this is not true. For example, Matthew 1 verse 21 states: "...thou shalt call his name JESUS: for he shall save his people from their sins." (Once again, the emphasis is mine.) We should pay close attention to that word "his" which is saying to us that "His" people are not just everyone on the entire Earth. God's people are the true born-again believers in Christ. God's people are His "elect" (Isaiah 42:1, Isaiah 65:9, Matthew 24:22, Matthew 24:31, Mark 13:27, John 15:16, Colossians 3:12, Titus 1:1, 1 Peter 1:2...) and not the entire multitude of the Earth. Only God's elect will be saved.
Another misinterpretation of John 3:16 (and indeed of the whole Gospel message) that is very common is the notion of believing in God. Mankind thinks that if he believes on God then he is safe. There is a problem with this however. Man cannot believe on God. Romans 3 verses 10 and 11 are explicit:
"As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God."
This is, I believe, a quotation of Isaiah 41 verse 26 where we read:
"Who hath declared from the beginning, that we may know? and beforetime, that we may say, [he is] righteous? yea, [there is] none that sheweth, yea, [there is] none that declareth, yea, [there is] none that heareth your words."
Since man cannot come to God on his own, as those verses teach, God has to do all of the work necessary for salvation. God said in John 14 verse 6 "...I am the way, the truth, and the life: no man cometh unto the Father, but by me." (Emphasis mine)
Other verses such as Matthew 19 verses 24 through 26 teach the same thing: "...It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God. When his disciples heard it, they were exceedingly amazed, saying, Who then can be saved? But Jesus beheld them, and said unto them, With men this is impossible; but with God all things are possible."
Evidences that God must do all the work for our salvation can be found in the Old Testament, in Leviticus 23 verse 3 we read:
"Six days shall work be done: but the seventh day [is] the Sabbath of rest, an holy convocation; ye shall do no work [therein]: it [is] the Sabbath of the LORD in all your dwellings."
The cessation of work on the Old Testament Sabbath day was pointing to the fact that Christ would do all the work necessary for salvation.
While man can do nothing to gain his salvation, by the same token he cannot do anything to lose his salvation. John 6:37 reads: "All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out." In the interests of avoiding confusion we should make a note that where it says "...him that cometh to me..." it is talking about those who God has already given a regenerate heart as a born-again believer.
John 6:37 is a profound argument that once he/she is saved, an elect person cannot lose his/her salvation.
Now what's this perishing that John 3:16 is talking about? If you ask the church, most likely what they will tell you is you will go to Purgatory for a thousand years (the Catholic church), or you will never find your purpose in life or some variation of that. And that is only if they admit that that Christ did not pay for the sins of the whole world in the first place. If they do not admit that, then they will say "God loves you and has a wonderful plan for your life!" And this, sadly, is not true for many, many people.
The perishing that God is talking about is eternal damnation in Hell in payment for your sins! Not failing to find your purpose in life! It is talking about being shut out of Heaven and under the wrath of God for eternity!
How terrible this is! It's impossible to be too scared by it. But it is true. Revelation 20 verses 12 through 15 explain the situation facing the unsaved at the end of the world:
"And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works. And death and hell were cast into the lake of fire. This is the second death. And whosoever was not found written in the book of life was cast into the lake of fire.
The "lake of fire" is eternal damnation, and that is what the unsaved will face at the end of the world. "...Whosoever was not found written in the book of life..." are the unsaved of the world.
"For the wages of sin [is] death; but the gift of God [is] eternal life through Jesus Christ our Lord." Romans 6:23
But God again gives the promise of eternal life to his elect "...through Jesus Christ..." once again indicating that Christ must do all the work as our redeemer and saviour.
May it be that God will have mercy on you.